Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$95.94	10.344%	$105.864	$105.86	$105.85	$105.90
Purchase #2	$148.27	9.592%	$162.4921	$162.49	$162.50	$162.50
Purchase #3	$85.25	3.360%	$88.1144	$88.11	$88.10	$88.10
Purchase #4	$50.83	4.359%	$53.0457	$53.05	$53.05	$53.00
Purchase #5	$230.30	12.386%	$258.825	$258.83	$258.85	$258.80
Purchase #6	$133.73	4.581%	$139.8562	$139.86	$139.85	$139.90
Purchase #7	$111.65	7.278%	$119.7759	$119.78	$119.80	$119.80
7 purchase totals =	$855.97		$927.9733	$927.98	$928.00	$928.00